Hydrocarbons such as oil and gas are produced from subterranean wells. Hydrocarbons were formed millions of years ago by deposit of decayed plant matter into underground rock formations. There may be water located in underground formations at levels above or below hydrocarbon-bearing rock formations. Water-bearing geological zones often are penetrated by such subterranean oil and gas wells. It is common in the case of both land-based wells and subsea wells to produce from the wellbore both undesirable water and desirable oil in a combined mixture or emulsion. In many instances, water is removed from the emulsion in a water-oil separation process after the combined emulsion has been removed from the wellbore. Such separation processes are referred to as processes to “break” such emulsions.
Emulsions may cause serious flow assurance problems in the oil and gas production industry. Strong mineral acids sometimes are used to break emulsions. However, in certain geological regions of the world it has been found that some of the produced oil/water emulsions are very difficult to break into component oil and aqueous fractions after the emulsion is brought forth from the wellbore. Some crude oils contain chemical species that are believed to prevent successful breaking of such emulsions, even after exposure of the formation fluids to conventional strong mineral acid demulsifiers.
For example, at deepwater subsea oil and gas fields in some regions of the world, a floating production unit (FPU) may be employed to provide heat and strongly acidic demulsifiers to break the emulsions into salable oil and water. Depending upon the chemical characterization of the subterranean formation and formation fluids, it may require exceptionally large amounts of strong mineral acids and applied heat energy to produce a separated crude oil.
A challenge in the industry is to find improved compositions and methods for reliably separating difficult to break emulsions with a reduced amount of expensive applied heat energy and with a reduced amount of applied chemicals. Furthermore, a challenge in the industry is to find compositions that can accomplish the breaking of such emulsions without damaging or compromising metallic equipment with strong mineral acids. Many conventional strong mineral acid compositions used for this purpose are detrimental to oilfield equipment and associated tubulars.
This disclosure is directed to improved emulsion separation methods, systems and compositions.